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The new normal: empirical estimates of future fire environments in the Pacific Northwest

A screen capture from an interactive time series mapping tool showing the normal fire environment projected for 2040 in the Okanogan-Wenatchee National Forest. Blue areas are projected to have low suitably for fires larger than 100 acres, yellow indicates moderate suitability, and red indicates environments that are likely to be highly suitable to large fires.

Pacific Northwest Region U.S. Forest Service; Oregon State University; Oregon Department of Forestry and National Interagency

Description

Large wildfires in the Pacific Northwest are increasingly frequent compared to the past three decades of the 20th century. These wildfires are products of their environment. As droughts become more common in much of the Western United States and temperatures warm, forest environments are becoming more suitable for large wildfires.

Forest Service scientists and collaborators extrapolated and contrasted what is considered today’s ‘‘normal” fire environment to what might be considered normal by the end of this century as a result of forecasted changes in climate. Their findings indicate more forest area in all ecoregions of the Pacific Northwest will be suitable for the occurrence of wildfire larger than 100 acres over the next century. The largest increases are projected to occur on federal lands, while private and state lands showed less. By the end of the century, the models predict shorter fire-rotation periods; cooler, moister forests are projected to experience larger magnitudes of change than warmer, drier forests.

Planning ahead.

This project yielded a set of time series maps that provide forest resource managers, fire protection agencies, and policymakers with empirical estimates of how much and where climate change might affect the geographic distribution of large wildfires and fire rotations. Areas where the fire environment is not likely to change much might serve as focal areas for fire refugia and reserves designed to maintain or restore older, denser, closed-canopy forests. Forests that are currently classified as moderately suitable for large wildfires, or are predicted to become so, may be places to focus active management to improve resilience to future wildfires. Management to ameliorate fire risk may be needed where forests have or are predicted to transition into higher wildfire suitability classes and, because of their location, also pose threats to infrastructure or valued forest resources, and where fire has not been as common.